The present invention relates to a process for preparing novel, monodisperse ion exchangers having chelating functional groups, and to the use of these.
U.S. Pat. No. 4,444,961 discloses a process for preparing monodisperse, macroporous chelating resins. In this process, halo-alkylated polymers are aminated and the aminated polymer is reacted with chloroacetic acid to give chelating resins of iminodiacetic acid type.
A disadvantage of this process is post-crosslinking at the haloalkylated bead polymers stage of the process and also at the subsequent aminomethylated bead polymers stage of the process. EP-A 481,603 describes the disadvantages of post-crosslinking arising at these two stages and a method for the minimization thereof.
The present invention provides hitherto unknown monodisperse chelating resins whose preparation avoids the haloalkylated intermediate stage, and also the use of these.
The novel process does away with post-crosslinking.
The novel products have a uniform structure. Surprisingly, it has been found that the absence of post-crosslinking allows a relatively high degree of substitution of the aromatic rings with functional groups to be achieved and thus a relatively high exchange capacity in the final product. The yield of final product, based on the monomers used, is moreover markedly higher than is the case with final products prepared according to the prior art.